Provided are a low-voltage image sensor and a method of driving a transfer transistor thereof, which are obtained by changing the structure and driving method of a typical transfer transistor of a 4-transistor CMOS transistor, and can eliminate the influence of a voltage or physical structure of a diffusion node on a reset or transfer operation of a photodiode. The image sensor includes a light receiving device for detecting light and a signal conversion unit for reading photocharge generated by the light receiving device to an external circuit. The signal conversion unit includes a transfer transistor including at least two gate electrodes. When the photocharge is transferred to a channel of a transfer gate electrode disposed closest to a photodiode, a transfer gate electrode disposed adjacent to a diffusion node remains turned off.